1. Field of the Invention
The present invention relates to apparatus and method for manufacturing an optical transmission module, and more particularly to apparatus and method for manufacturing an optical transmission module used in light communication systems such as optical LAN or optical CATV systems.
2. Related Background Art
An output laser beam from a semiconductor laser has a spread angle of .+-.20 degrees vertically and .+-.5 to .+-.10 degrees horizontally. Accordingly, when a semiconductor laser and an optical fiber are coupled together to manufacture an optical transmission module, they are usually coupled by lens coupling systems.
In a module structure called a pigtail type, the optical fiber is fixed to an optical fiber mount in a vicinity of the semiconductor laser which is fixed on a stem. In the pigtail type module, a position precision of .+-.0.2 to .+-.0.5 .mu.m is required particularly when a single mode ball fiber. In fixing the optical fiber, fusing metal such as solder is used and the optical fiber is finely positioned to a maximum output position while an optical output from the optical fiber is monitored.
However, when the optical fiber is soldered, the adjacent semiconductor laser is also heated and the optical output of the semiconductor laser changes with the temperature rise as shown in FIG. 3. Accordingly, it is not possible to discriminate the change of the optical output due to the displacement of the optical axis from that due to the temperature change of the semiconductor laser, by monitoring the optical output. Accordingly, in the past, it has been difficult to fix the optical fiber at an optimum position.